An animal species’ diet constitutes the basic ecology of that species and is indispensable for understanding its ecological niche. Crows (Corvus corone and C. macrorhynchos) gather at communal roosts in winter and regurgitate indigestible portions of food as pellets on the ground under the roost. We used pellet analysis to determine crows’ diets and compared them between agricultural (Joetsu region, Niigata) and urban areas (Tokyo) in 2002 winter, The pellets were classified into plant animal and artificial matter. The major food substance in both areas was plant matter. The pellets collected in the Joetsu region were shaped like bullets and contained primarily seeds of Oryza sativa and Rhus spp. The pellets collected in Tokyo had loose texture and were flattened, and contained plant matter such as fruits and berries of trees and shrubs, Second in frequency to plant matter was artificia1 matter consisting of small pieces of white or transparent plastic usually used for garbage bags. Artificial matter also contained aluminum foil and paper, a1l of which are used for food wrappings, suggesting their association with food scraps. In this study, we discussed the utility of crow pellets for teaching food webs and the environmental issues such as garbage disposal.
We observed oviposition behavior of the ectoparasitoid wasp, Euplectrus separatae that parasitized on the common army worm Pseudaletia separata. The female wasps always oviposit on the dorsal surface of three segments from the 3rd thoracic to the 2nd abdominal segment of the host. This oviposition behavior may be important to escape from the aggressive defense behavior of the host at the time of oviposition. We attempted to develop a new method because several experiments out of analyzed oviposition behavior patterns in E. separatae seemed to be appropriate as teaching materials for high school students. It is very difficult to practice all of the experiments on this wasp oviposition behavior in a class at high school but it is possible to carry out one or two parts of the experiments.
High school students in Aichi prefecture have observed the oviposition behavior of E. separatae. And they got the following conclusions as follows. (1) An extract of host frass by ethyl ether gave rise to the searching behavior of a female wasp. (2) As the female wasp found out her host, she mounted the posterior part of the host abdomen. As soon as the host moved forward, the female wasp also moved forward on the host’s body. The female wasp laid eggs after stopping near the host head (the first segment of abdomen). (3) The peristaltic movment of the host was the trigger for the female wasp to move forward.
Every student understood the meaning of the experiments on the wasp’s oviposition behavior. And most of the students could reach to the desired conclusions. Moreover as the time schedule is suitable, we judged this experiment of the wasp’s oviposition behavior is suitable for high school’s biology class.